Chairside CAD/CAM materials. Part 3: Cyclic fatigue parameters and lifetime predictions

Objectives

Chemical and mechanical degradation play a key role on the lifetime of dental restorative materials. Therefore, prediction of their long-term performance in the oral environment should base on fatigue, rather than inert strength data, as commonly observed in the dental material’s field. The objective of the present study was to provide mechanistic fatigue parameters of current dental CAD/CAM materials under cyclic biaxial flexure and assess their suitability in predicting clinical fracture behaviors.

Fracture strength testing of crowns made of CAD/CAM composite resins

Purpose

The purpose of this study was to ascertain whether computer aided design/computer aided manufacturing (CAD/CAM) composite resin crowns have sufficient strength to withstand the bite force of the molar teeth. The null hypothesis was that the fracture strength of CAD/CAM composite resin crowns is lower than the average maximum bite force of the molar tooth.

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization

Objective

A deeper understanding of the mechanical behavior of dental restorative materials requires an insight into the materials elastic constants and microstructure. Here we aim to use complementary methodologies to thoroughly characterize chairside CAD/CAM materials and discuss the benefits and limitations of different analytical strategies.

Mechanical degradation of contemporary CAD/CAM resin composite materials after water ageing

ObjectiveThe aim of the present study was to assess the effect of water storage on the quasi-static properties and cyclic fatigue behavior of four contemporary CAD/CAM resin composite materials.MethodsThe CAD/CAM resin composites Grandio Blocs, Lava^TM Ultimate, Cerasmart^TM and Brilliant Crios, as well as the direct resin composite Grandio SO, were evaluated. Rectangular plates were cut from the blocks or fabricated using a silicon mold to obtain specimens for fracture toughness (K_Ic, n = 10), biaxial strength (σ₀, n = 30) and cyclic fatigue testing (n = 30). Half of the specimens was stored for 24 h in dry conditions and the other half was aged for 60 days in distilled water at 37 °C. K_Ic was determined using the Compact-Tension (C(T)) method and σ₀ and cyclic fatigue were tested using the Ball-on-Three-Balls assembly. Additional disc-shaped specimens (n = 5) were produced to obtain water sorption curves of the materials. Weibull statistics and two-way ANOVA with Tukey’s post-hoc test were used for data assessment.ResultsThe highest water sorption was observed for Lava^TM Ultimate (42.6 μg/mm³), whereas Grandio SO displayed the lowest uptake (14 μg/mm³). A statistically significant drop in K_Ic and σ₀ was measured for all materials after water storage, except for the σ₀ of Cerasmart^TM. Water ageing had a dissimilar effect on the cyclic fatigue behavior, increasing the slow crack growth susceptibility of Lava^TM Ultimate, but decreasing it for Cerasmart^TM and Brilliant Crios.SignificanceContemporary CAD/CAM resin composites are susceptible to water driven degradative processes, although differences in filler content and resin matrix constitution play an important role in how it impacts their mechanical properties.     

Ceramic dental biomaterials and CAD/CAM technology: State of the art

PurposeCeramics are widely used as indirect restorative materials in dentistry because of their high biocompatibility and pleasing aesthetics. The objective is to review the state of the arts of CAD/CAM all-ceramic biomaterials.Study selectionCAD/CAM all-ceramic biomaterials are highlighted and a subsequent literature search was conducted for the relevant subjects using PubMed followed by manual search.ResultsDevelopments in CAD/CAM technology have catalyzed researches in all-ceramic biomaterials and their applications. Feldspathic glass ceramic and glass infiltrated ceramic can be fabricated by traditional laboratory methods or CAD/CAM. The advent of polycrystalline ceramics is a direct result of CAD/CAM technology without which the fabrication would not have been possible.ConclusionsThe clinical uses of these ceramics have met with variable clinical success. Multiple options are now available to the clinicians for the fabrication of aesthetic all ceramic restorations.     

CAD/CAM复合陶瓷材料表面处理的研究进展

随着CAD/CAM技术的不断发展,越来越多的CAD/CAM复合陶瓷材料被应用于口腔修复学,其远期修复效果很大程度取决于修复体的粘接强度,其中影响修复体与牙体粘接强度的主要因素就是修复体的表面处理,该文就CAD/CAM材料的表面处理的研究进展作一综述。     

Effect of different surface treatments on the biaxial flexure strength,Weibull characteristics,roughness, and surface topography of bonded CAD/CAM silica-based ceramics

ObjectiveTo investigate the influence of different surface treatments on biaxial flexure strength, roughness, and surface topography of lithium silicate/disilicate-based ceramics.Methods225 discs (?: 12 mm; 1.2 mm – ISO 6872) were made from three ceramics: IPS e.max CAD (LD – Ivoclar Vivadent), Suprinity (LSS - Vita) and Celtra Duo (LSC - Dentsply). The samples were randomly divided into 5 groups (n = 15): no treatment (C); 10% hydrofluoric acid + silane (HF); sandblasting Al₂O₃ + silane (SB); silicatization + silane (SC); and self-etching ceramic primer (SEP). After surface treatment, a resin cement layer was applied to the disc surface (RelyX U200, 3M ESPE), mechanical cycled (1.2 × 10⁶ cycles, 50 N, 3.8 Hz) and submitted to biaxial flexural strength test (1 mm/min, 1000 Kgf). Roughness, EDS and SEM were also performed. Data were analyzed by one-way ANOVA, Tukey test (5%) and Weibull.ResultsANOVA revealed that the “surface treatment” factor was significant for all ceramics (p < 0.05). The groups LD-HF (289.30 ± 40) LD-SEP (298. 87 ± 53.29), LSC-HF (195.51 ± 42.12), LSS-HF (269.58 ± 27.07) and LSS-SEP (207.45 ± 28.63) presented significantly higher biaxial flexure strength than respective control groups, except for the LSC-SEP (165.41 ± 33.86), which was statistically similar to the control. The Weibull modulus was significantly higher for the LD-SB, LSC-SC groups. Additionally, the LD-SB, LSC-SC and LSS-HF groups showed higher roughness compared to the other treatments.SignificanceHF etching followed by silanization and self-etching ceramic primer are the most suitable surface treatments for lithium silicate/disilicate-based glass-ceramics.     

Does artificial aging affect mechanical properties of CAD/CAM composite materials

Purpose

The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions.

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

PURPOSE

All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident.

MATERIALS AND METHODS

Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns.

RESULTS

The mean fracture strengths were as follows: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain.

CONCLUSION

The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.     

Additive CAD/CAM Process for Dental Prostheses

This article describes the evolution of a computer‐aided design/computer‐aided manufacturing (CAD/CAM) process where ceramic paste is deposited in a layer‐by‐layer sequence using a computer numerical control machine to build up core and fixed partial denture (FPD) structures (robocasting). Al₂O₃ (alumina) or ZrO₂ (Y‐TZP) are blended into a 0.8% aqueous solution of ammonium polyacrylate in a ratio of approximately 1:1 solid:liquid. A viscosifying agent, hydroxypropyl methylcellulose, is added to a concentration of 1% in the liquid phase, and then a counter polyelectrolyte is added to gel the slurry. There are two methods for robocasting crown structures (cores or FPD framework). One is for the core to be printed using zirconia ink without support materials, in which the stereolithography (STL) file is inverted (occlusal surface resting on a flat substrate) and built. The second method uses a fugitive material composed of carbon black codeposited with the ceramic material. During the sintering process, the carbon black is removed. There are two key challenges to successful printing of ceramic crowns by the robocasting technique. First is the development of suitable materials for printing, and second is the design of printing patterns for assembly of the complex geometry required for a dental restoration. Robocasting has room for improvement. Current development involves enhancing the automation of nozzle alignment for accurate support material deposition and better fidelity of the occlusal surface. An accompanying effort involves calculation of optimal support structures to yield the best geometric results and minimal material usage.     

Physical properties and wear behavior of CAD/CAM resin composite blocks containing S-PRG filler for restoring primary molar teeth

ObjectivesThis study aimed to develop computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks (RCBs) containing surface pre-reacted glass-ionomer (S-PRG) filler for primary molar teeth and evaluate their physical properties and wear resistance.MethodsExperimental CAD/CAM RCBs containing S-PRG filler for primary molar teeth (EB), a commercial CAD/CAM RCB (HC), two resin composites for primary teeth (BKP and BKZ) and one for permanent teeth (BⅡ) were used. Hardness tests, three-point bending tests, fracture toughness tests, and water absorption tests were conducted. Wear tests were conducted for these materials and stainless steel crowns (SSCs).ResultsThe Vickers hardness of EB was lower than that of HC (p < 0.05), and there was no significant difference among BKZ, BKP, and BⅡ (p > 0.05). After 1 week of water immersion, EB and HC showed greater flexural strength than the other materials (p < 0.05). EB showed greater fracture toughness than the other materials (p < 0.05). The water absorption of EB was lower than that of HC, BKZ, and BKP (p < 0.05), and greater than that of BⅡ (p < 0.05). Antagonist wear was significantly smaller in EB than in HC and BⅡ (p < 0.05), and significantly greater than in BKZ (p < 0.05). Antagonist wear could not be measured in SSC because of excessive wear that was out of range of the surface roughness tester.SignificanceThe CAD/CAM RCBs containing S-PRG filler for primary molar teeth developed in this study demonstrated adequate physical properties and wear performance, suggesting that they are suitable for restoration of primary molar teeth and could function in place of SSCs.     

Long-term tensile bond strength of differently cemented nanocomposite CAD/CAM crowns on dentin abutment

Objectives

To test the tensile bond strength of luted composite computer aided design/computer aided manufacturing (CAD/CAM) crowns after use of different adhesive systems combined with different resin composite cements on dentin abutments.

Methods

Human molars (n = 200) were embedded in acrylic resin, prepared in a standardized manner and divided into 20 groups (n = 10). The crowns were treated as follows: (i) Monobond Plus/Heliobond (MH), (ii) Ambarino P60 (AM), (iii) Visio.link (VL), (iv) VP connect (VP), and (v) non-treated as control groups (CG) and luted with Variolink II (VAR) or Clearfil SA Cement (CSA). Tensile bond strength (TBS) was measured initially (24 h water, 37 °C) and after aging (5000 thermal cycles, 5/55 °C). The failure types were evaluated after debonding. TBS values were analyzed using three-way and one-way ANOVA, followed by post hoc Scheffé-test, and two-sample Student's t-tests.

Results

Among VAR and after aging, CG presented significantly higher TBS (p = 0.007) than groups treated with MH, AM and VP. Other groups showed no impact of pre-treatment. A decrease of TBS values after thermal aging was observed within CSA: CG (p = 0.002), MH (p < 0.001), VL (p < 0.001), AM (p = 0.002), VP (p < 0.001) and within VAR: MH (p = 0.002) and AM (p = 0.014). Groups cemented with VAR showed significantly higher TBS then groups cemented with CSA: non-aged groups: CG (p < 0.001), and after thermal aging: CG (p = 0.003), MH (p < 0.001), VL (p = 0.005), VP (p = 0.010).

Significance

According to the study results nano-composite CAD/CAM crowns should be cemented with VAR. Pre-treatment is not necessary if the tested resin composite cements are used.     

Uniaxial/biaxial flexure strengths and elastic properties of resin-composite block materials for CAD/CAM

Objective

Comparing strengths under different loading conditions provides useful information on the mechanical behaviour of restorative materials under multiaxial masticatory loading in the oral cavity. The aims of this study was to investigate the flexural strengths and the reliability of resin-composite blocks for CAD/CAM by uniaxial and biaxial flexure tests and to compare the elastic properties measured by different methods including digital image correlation (DIC).

The use of CAD/CAM in dentistry

Computer-aided design (CAD) and computer-aided manufacturing (CAM) have become an increasingly popular part of dentistry over the past 25 years. The technology, which is used in both the dental laboratory and the dental office, can be applied to inlays, onlays, veneers, crowns, fixed partial dentures, implant abutments, and even full-mouth reconstruction. This article discusses the history of CAD/CAM in dentistry and gives an overview of how it works. It also provides information on the advantages and disadvantages, describes the main products available, discusses how to incorporate the new technology into your practice, and addresses future applications.     

口腔修复 CAD/CAM系统中的虚拟牙合架

随着数字化技术在口腔临床的广泛应用,虚拟(牙合)架已经成为口腔修复 CAD／CAM系统中的一个重要工具。本文从虚拟(牙合)架的分类、特点和设置3个方面对其进行了全面介绍,并结合临床实际和国内现有商用虚拟(牙合)架产品进行了点评。     

渗透玻璃对牙科CAD/CAM用氧化铝玻璃复合体颜色的影响

目的:测定牙科CAD/CAM用氧化铝玻璃复合体系统的颜色,为临床应用奠定基础。方法:选用自行研制的CAD/CAM氧化铝玻璃复合体的AG1、AG2、AG3、AG4色系及VitaIn CeramAL1、AL2、AL3、AL4色系的渗透玻璃粉,对牙科CAD/CAM用氧化铝块进行渗透,制作 10mm×10mm,厚度分别为 0. 5、1、1. 5mm的颜色测量试样,采用分光测色计对颜色进行测定。结果:以 1mm厚度样本为标准,VitaIn CeramAlumina范围为L*: 69. 39~78. 41,a*: 1. 82~4. 02,b*: 18. 35 ~24. 42;CAD/CAM用氧化铝玻璃复合体系统的颜色范围为L*: 68. 80~78. 44,a*: 1. 32~4. 75,b*: 16. 86~21. 86。不同的是AG3铝瓷的b*值和饱和度较AL3铝瓷低,a*值较高;AG1和AG2铝瓷的b*值和饱和度较AL1和AL2铝瓷偏低。2种体系的可见光谱反射率相近。结论: CAD/CAM氧化铝玻璃复合体色系与VitaIn CeramAlumina材料色系的颜色范围近似,可以满足与表面饰瓷颜色匹配的要求。     

The fracture resistance of a CAD/CAM Resin Nano Ceramic (RNC) and a CAD ceramic at different thicknesses

Objectives

This study aimed to investigate the influence of restoration thickness to the fracture resistance of adhesively bonded Lava™ Ultimate CAD/CAM, a Resin Nano Ceramic (RNC), and IPS e.max CAD ceramic.

Methods

Polished Lava™ Ultimate CAD/CAM (Group L), sandblasted Lava™ Ultimate CAD/CAM (Group LS), and sandblasted IPS e.max CAD (Group ES) discs (n = 8, Ø = 10 mm) with a thickness of respectively 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, and 3.0 mm were cemented to corresponding epoxy supporting discs, achieving a final thickness of 3.5 mm. All the 120 specimens were loaded with a universal testing machine at a crosshead speed of 1 mm/min. The load (N) at failure was recorded as fracture resistance. The stress distribution for 0.5 mm restorative discs of each group was analyzed by Finite Element Analysis (FEA). The results of facture resistances were analyzed by one-way ANOVA and regression.

Results

For the same thickness of testing discs, the fracture resistance of Group L was always significantly lower than the other two groups. The 0.5 mm discs in Group L resulted in the lowest value of 1028 (112) N. There was no significant difference between Group LS and Group ES when the restoration thickness ranged between 1.0 mm and 2.0 mm. There was a linear relation between fracture resistance and restoration thickness in Group L (R = 0.621, P < 0.001) and in Group ES (R = 0.854, P < 0.001). FEA showed a compressive permanent damage in all groups.

Significance

The materials tested in this in vitro study with the thickness above 0.5 mm could afford the normal bite force. When Lava Ultimate CAD/CAM is used, sandblasting is suggested to get a better bonding.     

Adhesion procedure for CAD/CAM resin crown bonding: Reduction of bond strengths due to artificial saliva contamination

Purpose

The present study aimed to elucidate how saliva contamination affects microtensile bond strength of resin cement to CAD/CAM resin blocks and identify a decontamination method that can restore original bond strength.